This invention relates to a method for the preparation of alkyl or aryl halofluoroalkyl ethers.
Traditionally, dihydrocarbyl ethers such as arylalkyl ethers are prepared by the Williamson synthesis. In the Williamson synthesis, an alkyl halide or substituted alkyl halide is reacted with a sodium alkoxide or a sodium phenoxide to form the corresponding alkyl ether or aryl alkyl ether. The Williamson synthesis simply involves nucleophilic substitution of an alkoxide ion or a phenoxide ion for a halide ion.
Nucleophilic displacement of halogen ions from alkyl halides is a well-known reaction and displacement proceeds in the order F&lt;&lt;Cl&lt;Br&lt;I. Halogens on carbons beta to the reaction site usually retard the displacement. R. D. Chambers, Fluorine in Organic Chemistry, at 98 (1973). On the other hand, perfluoroalkanes and some of their chloro derivatives and to a lesser extent, bromo derivatives, are extremely resistant to nucleophilic attack.
W. J. Pummer and L. A. Wall, in the July 1963 SPE Transactions, have reported on the synthesis of 1,2,2,-trifluorovinyl phenyl ether and 1,2,2-trifluorovinyl perfluorophenyl ether in studies of high temperature polymers. Two methods were discussed. First, 1,1,2,2-tetrafluoroethyl phenyl ether was formed by reaction of phenoxide with tetrafluoroethylene and was then dehydrofluorinated under a variety of conditions. Formation of the desired vinyl ether was poor, usually resulting in yields of 5 percent or less. The second method was the reaction of phenoxide with tetrafluoroethylene under extremely anhydrous conditions. This was found to be the preferred method using mixed solvents, but yields still did not exceed 35 percent even under the best conditions.
In view of the aforementioned deficiencies of currently known techniques for making certain fluorovinyl phenyl ethers and their precursors, it is highly desirable to provide a method for preparing such precursors in yields greater than 35 percent.